Update README.md

Author: winscripter

README.md

@@ -41,7 +41,7 @@ File1.cs
 .editorconfig
 ```
 
-### Writing (applies to Slnx 2.0 and later)
+### Writing (applies to Slnx 2.0, see below code block for Slnx 3.0)
 ```cs
 using Slnx;
 using System.Text.Json;
@@ -70,6 +70,19 @@ var model = SlnxModel.Load(File.ReadAllText("OutputSlnx.txt"));
 Console.WriteLine(JsonSerializer.Serialize(model));
 ```
 
+Note: The constructor of the `Project` class was slightly changed. Change this:
+```cs
+// ...
+folder.AddProject(new Project("./DockerCompose/DockerCompose.dcproj", typeGuid: Guid.NewGuid(), config: new(solution: "*|*", project: "*|*|Deploy")));
+var moreFolders = new Folder("C++");
+```
+to:
+```cs
+// ...
+folder.AddProject(new Project("./DockerCompose/DockerCompose.dcproj", /*HERE -->*/type: Guid.NewGuid().ToString(), /*<-- HERE*/ config: new(solution: "*|*", project: "*|*|Deploy")));
+var moreFolders = new Folder("C++");
+```
+
 Starting with Slnx 3.0, you can convert `SlnxModel` to `string` asynchronously:
 ```cs
 // ...